3vw5
Crystal structure of sugar epimerase from ruminal bacterium
Structural highlights
FunctionCEEP_RUMAL Catalyzes the reversible epimerization of cellobiose to 4-O-beta-D-glucopyranosyl-D-mannose (Glc-Man). Can also epimerize cellotriose to Glc-Glc-Man, cellotetraose to Glc-Glc-Glc-Man, and lactose to epilactose.[HAMAP-Rule:MF_00929][1] [2] Publication Abstract from PubMedEnzymatic epimerization is an important modification for carbohydrates to acquire diverse functions attributable to their stereoisomers. Cellobiose 2-epimerase (CE) catalyzes interconversion between d-glucose and d-mannose residues at the reducing end of beta-1,4-linked oligosaccharides. Here, we solved the structure of Ruminococcus albus CE (RaCE). The structure of RaCE showed strong similarity to those of N-acetyl-D-glucosamine 2-epimerase and aldose-ketose isomerase YihS with a high degree of conservation of residues around the catalytic center, although sequence identity between them is low. Based on structural comparison, we found that His184 is required for RaCE activity as the third histidine added to two essential histidines in other sugar epimerases/isomerases. This finding was confirmed by mutagenesis, suggesting a new catalytic mechanism for CE involving three histidines. Crystal structure of Ruminococcus albus cellobiose 2-epimerase: structural insights into epimerization of unmodified sugar.,Fujiwara T, Saburi W, Inoue S, Mori H, Matsui H, Tanaka I, Yao M FEBS Lett. 2013 Apr 2;587(7):840-6. doi: 10.1016/j.febslet.2013.02.007. Epub 2013, Feb 24. PMID:23462136[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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